discounts now work well

assets/views/admin/catalog/discount_form.html

@@ -15,82 +15,80 @@
   {{ ui::button(variant="outline-secondary", label=t(key="cancel", lang=lang | default(value='sk')), href="/admin/catalog/products?audience=" ~ audience, size="px-3 py-2 text-sm") }}
 </div>
 
+{# One discount row per option (variant). Each row picks a fixed sale price or a   #}
+{# percentage off its own regular price; a blank input clears that option's        #}
+{# discount. Both the fixed and percent inputs always submit (the server reads the #}
+{# active mode); rows are pre-filled from `rows` (DB values, or submitted values   #}
+{# when repainting after a validation error) and indexed as v[<variant id>][...].  #}
+<script id="discount-data" type="application/json">{{ rows | json_encode() | safe }}</script>
+
 <form method="post" action="/admin/catalog/products/{{ product.id }}/discount?audience={{ audience }}"
-  x-data="{
+  x-data="discountEditor(JSON.parse(document.getElementById('discount-data').textContent))"
-    mode: '{{ mode }}',
+  class="mt-6 max-w-2xl space-y-5">
-    fixed: '{{ fixed }}',
-    percent: '{{ percent }}',
-    regular: {{ product.regular_cents }},
-    num(v) { let n = parseFloat(String(v).replace(',', '.')); return isFinite(n) ? n : null; },
-    get afterCents() {
-      if (this.mode === 'percent') {
-        let p = this.num(this.percent); if (p === null) return null;
-        return this.regular - Math.round(this.regular * p / 100);
-      }
-      let f = this.num(this.fixed); if (f === null) return null;
-      return Math.round(f * 100);
-    },
-    money(c) { return (c / 100).toFixed(2); },
-    get valid() { let a = this.afterCents; return a !== null && a > 0 && a < this.regular; },
-    get percentOff() { let a = this.afterCents; return (a === null || this.regular <= 0) ? null : Math.round((this.regular - a) / this.regular * 100); }
-  }"
-  class="mt-6 max-w-md space-y-5 rounded-radius border border-outline bg-surface p-6 dark:border-outline-dark dark:bg-surface-dark-alt">
   {{ ui::csrf_field() }}
 
   {% if error %}
   {{ ui::alert_danger(message=t(key=error, lang=lang | default(value='sk'))) }}
   {% endif %}
 
-  <div class="flex items-center justify-between gap-3 rounded-radius bg-surface-alt px-4 py-3 dark:bg-surface-dark/40">
+  <template x-for="row in rows" :key="row.id">
-    <span class="text-sm text-on-surface/70 dark:text-on-surface-dark/70">{{ t(key="price", lang=lang | default(value='sk')) }}</span>
+    <div class="space-y-4 rounded-radius border border-outline bg-surface p-5 dark:border-outline-dark dark:bg-surface-dark-alt">
-    <span class="font-semibold tabular-nums text-on-surface-strong dark:text-on-surface-dark-strong">{{ product.regular_price }} {{ product.currency }}</span>
+      <div class="flex items-center justify-between gap-3">
-  </div>
+        <span class="font-semibold text-on-surface-strong dark:text-on-surface-dark-strong"
+          x-text="row.label || ('#' + row.id)"></span>
+        <span class="text-sm tabular-nums text-on-surface/70 dark:text-on-surface-dark/70">
+          {{ t(key="price", lang=lang | default(value='sk')) }}:
+          <span x-text="row.regular_price"></span> <span x-text="row.currency"></span>
+        </span>
+      </div>
 
-  <!-- mode toggle -->
+      <input type="hidden" :name="`v[${row.id}][mode]`" :value="row.mode">
-  <div class="grid grid-cols-2 gap-2">
-    <label class="flex cursor-pointer items-center justify-center gap-2 rounded-radius border px-3 py-2 text-sm transition"
-      :class="mode === 'fixed' ? 'border-primary bg-primary/10 text-on-surface-strong dark:border-primary-dark dark:bg-primary-dark/10 dark:text-on-surface-dark-strong' : 'border-outline text-on-surface dark:border-outline-dark dark:text-on-surface-dark'">
-      <input type="radio" name="mode" value="fixed" x-model="mode" class="sr-only">
-      {{ t(key="discount-mode-fixed", lang=lang | default(value='sk')) }}
-    </label>
-    <label class="flex cursor-pointer items-center justify-center gap-2 rounded-radius border px-3 py-2 text-sm transition"
-      :class="mode === 'percent' ? 'border-primary bg-primary/10 text-on-surface-strong dark:border-primary-dark dark:bg-primary-dark/10 dark:text-on-surface-dark-strong' : 'border-outline text-on-surface dark:border-outline-dark dark:text-on-surface-dark'">
-      <input type="radio" name="mode" value="percent" x-model="mode" class="sr-only">
-      {{ t(key="discount-mode-percent", lang=lang | default(value='sk')) }}
-    </label>
-  </div>
 
-  <!-- fixed price input -->
+      <div class="grid gap-4 sm:grid-cols-2">
-  <div class="space-y-1.5" x-show="mode === 'fixed'">
+        <!-- mode toggle -->
-    <label for="sale_price" class="text-sm font-medium text-on-surface-strong dark:text-on-surface-dark-strong">{{ t(key="sale-price", lang=lang | default(value='sk')) }}</label>
+        <div class="grid grid-cols-2 gap-2">
-    {{ ui::input(name="sale_price", id="sale_price", value=fixed, placeholder="0.00", attrs='inputmode="decimal" x-model="fixed"') }}
+          <label class="flex cursor-pointer items-center justify-center gap-2 rounded-radius border px-3 py-2 text-sm transition"
-  </div>
+            :class="row.mode === 'fixed' ? 'border-primary bg-primary/10 text-on-surface-strong dark:border-primary-dark dark:bg-primary-dark/10 dark:text-on-surface-dark-strong' : 'border-outline text-on-surface dark:border-outline-dark dark:text-on-surface-dark'">
+            <input type="radio" :name="`mode-ui-${row.id}`" value="fixed" x-model="row.mode" class="sr-only">
+            {{ t(key="discount-mode-fixed", lang=lang | default(value='sk')) }}
+          </label>
+          <label class="flex cursor-pointer items-center justify-center gap-2 rounded-radius border px-3 py-2 text-sm transition"
+            :class="row.mode === 'percent' ? 'border-primary bg-primary/10 text-on-surface-strong dark:border-primary-dark dark:bg-primary-dark/10 dark:text-on-surface-dark-strong' : 'border-outline text-on-surface dark:border-outline-dark dark:text-on-surface-dark'">
+            <input type="radio" :name="`mode-ui-${row.id}`" value="percent" x-model="row.mode" class="sr-only">
+            {{ t(key="discount-mode-percent", lang=lang | default(value='sk')) }}
+          </label>
+        </div>
 
-  <!-- percentage input -->
+        <!-- value input: both fields stay in the DOM and submit; the server reads
-  <div class="space-y-1.5" x-show="mode === 'percent'">
+             whichever matches the row's mode -->
-    <label for="percent" class="text-sm font-medium text-on-surface-strong dark:text-on-surface-dark-strong">{{ t(key="discount-percent", lang=lang | default(value='sk')) }}</label>
+        <div class="space-y-1.5">
-    {{ ui::input(name="percent", id="percent", value=percent, placeholder="0", attrs='inputmode="decimal" min="0" max="100" x-model="percent"') }}
+          <div x-show="row.mode === 'fixed'">
-  </div>
+            <label class="text-sm font-medium text-on-surface-strong dark:text-on-surface-dark-strong">{{ t(key="sale-price", lang=lang | default(value='sk')) }}</label>
+            <input :name="`v[${row.id}][fixed]`" x-model="row.fixed" inputmode="decimal" placeholder="0.00"
+              class="w-full rounded-radius border border-outline bg-surface-alt px-4 py-2 text-sm text-on-surface focus-visible:outline-2 focus-visible:outline-offset-2 focus-visible:outline-primary dark:border-outline-dark dark:bg-surface-dark-alt/50 dark:text-on-surface-dark dark:focus-visible:outline-primary-dark">
+          </div>
+          <div x-show="row.mode === 'percent'">
+            <label class="text-sm font-medium text-on-surface-strong dark:text-on-surface-dark-strong">{{ t(key="discount-percent", lang=lang | default(value='sk')) }}</label>
+            <input :name="`v[${row.id}][percent]`" x-model="row.percent" inputmode="decimal" min="0" max="100" placeholder="0"
+              class="w-full rounded-radius border border-outline bg-surface-alt px-4 py-2 text-sm text-on-surface focus-visible:outline-2 focus-visible:outline-offset-2 focus-visible:outline-primary dark:border-outline-dark dark:bg-surface-dark-alt/50 dark:text-on-surface-dark dark:focus-visible:outline-primary-dark">
+          </div>
+        </div>
+      </div>
 
-  <!-- live preview -->
+      <!-- live preview -->
-  <div x-show="afterCents !== null" x-cloak
+      <div x-show="afterCents(row) !== null" x-cloak
-    class="space-y-2 rounded-radius border border-outline bg-surface-alt px-4 py-3 dark:border-outline-dark dark:bg-surface-dark/40">
+        class="flex flex-wrap items-center justify-between gap-3 rounded-radius border border-outline bg-surface-alt px-4 py-2.5 text-sm dark:border-outline-dark dark:bg-surface-dark/40">
-    <div class="flex items-center justify-between gap-3 text-sm">
+        <span class="text-on-surface/70 dark:text-on-surface-dark/70">{{ t(key="discount-preview-after", lang=lang | default(value='sk')) }}</span>
-      <span class="text-on-surface/70 dark:text-on-surface-dark/70">{{ t(key="discount-preview-before", lang=lang | default(value='sk')) }}</span>
+        <span class="flex items-center gap-2">
-      <span class="tabular-nums text-on-surface/60 line-through dark:text-on-surface-dark/60"><span x-text="money(regular)"></span> {{ product.currency }}</span>
+          <span class="tabular-nums text-on-surface/50 line-through dark:text-on-surface-dark/50" x-text="money(row.regular_cents) + ' ' + row.currency"></span>
+          <span class="text-base font-semibold tabular-nums" :class="valid(row) ? 'text-danger' : 'text-on-surface/40 dark:text-on-surface-dark/40'"
+            x-text="money(afterCents(row)) + ' ' + row.currency"></span>
+          <span x-show="valid(row)" class="text-xs text-on-surface/60 dark:text-on-surface-dark/60" x-text="'(−' + percentOff(row) + '%)'"></span>
+        </span>
+      </div>
+      <p x-show="afterCents(row) !== null && !valid(row)" class="text-xs text-danger">{{ t(key="discount-below-regular", lang=lang | default(value='sk')) }}</p>
     </div>
-    <div class="flex items-center justify-between gap-3">
+  </template>
-      <span class="text-sm text-on-surface/70 dark:text-on-surface-dark/70">{{ t(key="discount-preview-after", lang=lang | default(value='sk')) }}</span>
-      <span class="text-lg font-semibold tabular-nums" :class="valid ? 'text-danger' : 'text-on-surface/40 dark:text-on-surface-dark/40'">
-        <span x-text="money(afterCents)"></span> {{ product.currency }}
-      </span>
-    </div>
-    <div x-show="valid" class="flex items-center justify-between gap-3 text-xs text-on-surface/60 dark:text-on-surface-dark/60">
-      <span>{{ t(key="discount-preview-save", lang=lang | default(value='sk')) }}</span>
-      <span class="tabular-nums"><span x-text="money(regular - afterCents)"></span> {{ product.currency }} (−<span x-text="percentOff"></span>%)</span>
-    </div>
-    <p x-show="!valid" class="text-xs text-danger">{{ t(key="discount-below-regular", lang=lang | default(value='sk')) }}</p>
-  </div>
 
   <div class="flex flex-wrap gap-3 pt-2">
     {{ ui::button(label=t(key="save", lang=lang | default(value='sk')), type="submit", attrs=`onclick="return confirm('` ~ t(key="discount-apply-confirm", lang=lang | default(value='sk')) ~ `')"`) }}
@@ -99,4 +97,36 @@
     {% endif %}
   </div>
 </form>
+
+<script>
+  function discountEditor(initial) {
+    return {
+      rows: (initial || []).map(r => ({
+        id: r.id,
+        label: r.label || '',
+        regular_cents: r.regular_cents,
+        regular_price: r.regular_price,
+        currency: r.currency,
+        mode: r.mode || 'fixed',
+        fixed: r.fixed || '',
+        percent: r.percent || '',
+      })),
+      num(v) { let n = parseFloat(String(v).replace(',', '.')); return isFinite(n) ? n : null; },
+      money(c) { return (c / 100).toFixed(2); },
+      afterCents(row) {
+        if (row.mode === 'percent') {
+          let p = this.num(row.percent); if (p === null) return null;
+          return row.regular_cents - Math.round(row.regular_cents * p / 100);
+        }
+        let f = this.num(row.fixed); if (f === null) return null;
+        return Math.round(f * 100);
+      },
+      valid(row) { let a = this.afterCents(row); return a !== null && a > 0 && a < row.regular_cents; },
+      percentOff(row) {
+        let a = this.afterCents(row);
+        return (a === null || row.regular_cents <= 0) ? null : Math.round((row.regular_cents - a) / row.regular_cents * 100);
+      },
+    };
+  }
+</script>
 {% endblock content %}

assets/views/admin/catalog/product_form.html

@@ -60,7 +60,7 @@
         {# items-end bottom-aligns every input regardless of how many lines each
            label takes, so the row stays aligned even with the "(optional)" notes. #}
         <div class="grid flex-1 grid-cols-2 gap-3 sm:grid-cols-12 sm:items-end">
-          <div class="space-y-1 col-span-2 sm:col-span-4">
+          <div class="space-y-1 col-span-2 sm:col-span-6">
             <label class="{{ sublabel }} block truncate">{{ t(key="option-label", lang=lang | default(value='sk')) }}{{ opt }}</label>
             <input :name="`variants[${i}][label]`" x-model="row.label" class="{{ inp }}" placeholder="napr. 10cm x 13cm">
           </div>
@@ -76,10 +76,6 @@
             <label class="{{ sublabel }} block truncate">{{ t(key="price", lang=lang | default(value='sk')) }}</label>
             <input :name="`variants[${i}][price]`" x-model="row.price" inputmode="decimal" required class="{{ inp }}" placeholder="0.00">
           </div>
-          <div class="space-y-1 sm:col-span-2">
-            <label class="{{ sublabel }} block truncate">{{ t(key="business-price", lang=lang | default(value='sk')) }}{{ opt }}</label>
-            <input :name="`variants[${i}][business_sale]`" x-model="row.business_sale" inputmode="decimal" class="{{ inp }}" placeholder="—">
-          </div>
         </div>
 
         <button type="button" @click="remove(i)"
@@ -90,7 +86,7 @@
 
   <script>
     function variantEditor(initial) {
-      const blank = () => ({ id: '', label: '', sku: '', stock: '', price: '', business_sale: '' });
+      const blank = () => ({ id: '', label: '', sku: '', stock: '', price: '' });
       return {
         rows: (initial || []).map(r => ({
           id: r.id || '',
@@ -98,7 +94,6 @@
           sku: r.sku || '',
           stock: (r.stock === null || r.stock === undefined) ? '' : r.stock,
           price: r.price || '',
-          business_sale: r.business_sale || '',
         })),
         init() { if (this.rows.length === 0) this.add(); },
         add() { this.rows.push(blank()); },

assets/views/admin/catalog/products.html

@@ -138,6 +138,14 @@
         <td class="px-4 py-3">
           <div class="flex flex-wrap justify-end gap-2">
             {{ ui::button(variant="outline-secondary", label=t(key="edit", lang=lang | default(value='sk')), href="/admin/catalog/products/" ~ product.id ~ "/edit", size="px-3 py-1.5 text-xs") }}
+            {{ ui::button(variant="outline-secondary", label=t(key="set-discount", lang=lang | default(value='sk')), href="/admin/catalog/products/" ~ product.id ~ "/discount/edit?audience=" ~ audience, size="px-3 py-1.5 text-xs") }}
+            {% if product.on_sale %}
+            <form method="post" action="/admin/catalog/products/{{ product.id }}/discount/remove?audience={{ audience }}"
+              onsubmit="return confirm('{{ t(key="discount-remove-confirm", lang=lang | default(value='sk')) }}')">
+              {{ ui::csrf_field() }}
+              {{ ui::button(variant="outline-danger", label=t(key="remove-discount", lang=lang | default(value='sk')), type="submit", size="px-3 py-1.5 text-xs") }}
+            </form>
+            {% endif %}
             {{ ui::button(variant="outline-secondary", label=t(key="view", lang=lang | default(value='sk')), href="/shop/" ~ product.slug, size="px-3 py-1.5 text-xs") }}
             <form method="post" action="/admin/catalog/products/{{ product.id }}/delete"
               onsubmit="return confirm('{{ t(key="confirm-delete", lang=lang | default(value='sk')) }}')">

src/controllers/admin_products.rs

@@ -26,7 +26,7 @@ use crate::{
     },
     shared::{
         guard,
-        money::{format_bp, format_price, parse_price_to_cents},
+        money::{format_bp, format_price, parse_percent, parse_price_to_cents},
         pricing,
         slug::{slugify, unique_slug},
     },
@@ -105,30 +105,9 @@ struct VariantInput {
     /// `None` = available but not inventory-tracked.
     stock: Option<i32>,
     price_cents: i64,
-    business_sale_cents: Option<i64>,
     position: i32,
 }
 
-/// The optional business-sale price field on a variant row: blank means "no
-/// business quick-sale", a value must parse and be below the regular price.
-fn parse_optional_sale(
-    form: &MultipartForm,
-    i: usize,
-    key: &str,
-    price_cents: i64,
-) -> Result<Option<i64>> {
-    let Some(raw) = form.text(&format!("variants[{i}][{key}]")) else {
-        return Ok(None);
-    };
-    let cents = parse_price_to_cents(&raw)?;
-    if cents <= 0 || cents >= price_cents {
-        return Err(Error::BadRequest(
-            "a sale price must be positive and below the regular price".to_string(),
-        ));
-    }
-    Ok(Some(cents))
-}
-
 /// Parse the repeated variant rows from the form, in submission order. Blank
 /// rows (no price and no label) are skipped; at least one valid row is required.
 fn parse_variants(form: &MultipartForm) -> Result<Vec<VariantInput>> {
@@ -168,7 +147,6 @@ fn parse_variants(form: &MultipartForm) -> Result<Vec<VariantInput>> {
                     .ok_or_else(|| Error::BadRequest("stock must be 0 or more".to_string()))?,
             ),
         };
-        let business_sale_cents = parse_optional_sale(form, i, "business_sale", price_cents)?;
         let id = form
             .text(&format!("variants[{i}][id]"))
             .and_then(|s| s.parse::<i32>().ok());
@@ -179,7 +157,6 @@ fn parse_variants(form: &MultipartForm) -> Result<Vec<VariantInput>> {
             sku,
             stock,
             price_cents,
-            business_sale_cents,
             position: out.len() as i32,
         });
     }
@@ -197,9 +174,9 @@ fn apply_variant(active: &mut product_variants::ActiveModel, input: &VariantInpu
     active.sku = Set(input.sku.clone());
     active.stock = Set(input.stock);
     active.price_cents = Set(input.price_cents);
-    // The per-variant public sale price was removed from the UI; keep it cleared.
+    // Discounts (public + business sale) are owned by the discount page and keyed
-    active.sale_price_cents = Set(None);
+    // per option/audience; the product form must leave those columns untouched so
-    active.business_sale_price_cents = Set(input.business_sale_cents);
+    // it never clobbers a discount. New variants default them to NULL.
     active.position = Set(input.position);
 }
 
@@ -257,7 +234,6 @@ fn variant_form_json(variant: &product_variants::Model) -> serde_json::Value {
         "sku": variant.sku,
         "stock": variant.stock,
         "price": format_price(variant.price_cents),
-        "business_sale": variant.business_sale_price_cents.map(format_price),
     })
 }
 
@@ -340,9 +316,13 @@ async fn index(
                 .sum::<i32>()
                 .to_string()
         };
+        // The product is "on sale" for this audience if any option carries a
+        // discount; the per-option amounts live on the discount page.
+        let on_sale = variants.iter().any(|v| current_value(v, audience).is_some());
         rows.push(product_row(
             product,
             priced,
+            on_sale,
             variants.len(),
             stock_display,
             image,
@@ -373,6 +353,7 @@ async fn index(
 fn product_row(
     product: &products::Model,
     effective: &pricing::PricedProduct,
+    on_sale: bool,
     variant_count: usize,
     stock_display: String,
     image: Option<String>,
@@ -390,6 +371,7 @@ fn product_row(
         "image": image,
         "category_name": category_name,
         "regular_price": format_price(effective.regular_cents),
+        "on_sale": on_sale,
         "effective_price": format_price(effective.price_cents),
         "effective_reduced": effective.is_reduced(),
         "effective_percent_off": percent_off(effective.regular_cents, effective.price_cents),
@@ -619,6 +601,30 @@ fn list_redirect(audience: &str) -> Result<Response> {
     format::redirect(&format!("/admin/catalog/products?audience={audience}"))
 }
 
+/// Resolve a percentage off the regular price into a fixed sale price in cents.
+fn percent_to_sale_cents(regular_cents: i64, percent: f64) -> i64 {
+    let off = (regular_cents as f64 * percent / 100.0).round() as i64;
+    regular_cents - off
+}
+
+/// Which discount value an audience tab sees on a variant.
+fn current_value(variant: &product_variants::Model, audience: &str) -> Option<i64> {
+    if audience == BUSINESS {
+        variant.business_sale_price_cents
+    } else {
+        variant.sale_price_cents
+    }
+}
+
+/// Set the discount column on a variant for a given audience.
+fn set_value(active: &mut product_variants::ActiveModel, audience: &str, value: Option<i64>) {
+    if audience == BUSINESS {
+        active.business_sale_price_cents = Set(value);
+    } else {
+        active.sale_price_cents = Set(value);
+    }
+}
+
 /// Percent off the regular price, rounded to a whole number.
 fn percent_off(regular_cents: i64, sale_cents: i64) -> i64 {
     if regular_cents <= 0 {
@@ -742,6 +748,231 @@ async fn sync_profiles(
     list_redirect(audience)
 }
 
+// --- Per-variant discounts ---------------------------------------------------
+//
+// Each product is sold as one or more options (variants). A discount can be set
+// on every option individually, for the active audience: personal writes the
+// public `sale_price_cents`, business writes `business_sale_price_cents`. Per
+// option the admin picks a fixed sale price or a percentage off the regular
+// price; an empty value clears that option's discount.
+
+/// One option row in the discount form. Carries enough to pre-fill the editor
+/// and to survive a validation-error round-trip.
+struct DiscountRow {
+    id: i32,
+    label: String,
+    regular_cents: i64,
+    mode: String,
+    fixed: String,
+    percent: String,
+    has_discount: bool,
+}
+
+impl DiscountRow {
+    /// Pre-fill from the discount stored for this audience.
+    fn from_db(v: &product_variants::Model, audience: &str) -> Self {
+        let sale = current_value(v, audience);
+        DiscountRow {
+            id: v.id,
+            label: v.label.clone(),
+            regular_cents: v.price_cents,
+            mode: "fixed".to_string(),
+            fixed: sale.map(format_price).unwrap_or_default(),
+            percent: String::new(),
+            has_discount: sale.is_some(),
+        }
+    }
+
+    /// Pre-fill from the submitted values, to repaint the form after an error.
+    fn from_submitted(
+        v: &product_variants::Model,
+        audience: &str,
+        pairs: &HashMap<String, String>,
+    ) -> Self {
+        let get = |key: &str| {
+            pairs
+                .get(&format!("v[{}][{key}]", v.id))
+                .map(|s| s.trim().to_string())
+                .unwrap_or_default()
+        };
+        let mode = get("mode");
+        DiscountRow {
+            id: v.id,
+            label: v.label.clone(),
+            regular_cents: v.price_cents,
+            mode: if mode == "percent" {
+                mode
+            } else {
+                "fixed".to_string()
+            },
+            fixed: get("fixed"),
+            percent: get("percent"),
+            has_discount: current_value(v, audience).is_some(),
+        }
+    }
+
+    fn to_json(&self, currency: &str) -> serde_json::Value {
+        json!({
+            "id": self.id,
+            "label": self.label,
+            "regular_cents": self.regular_cents,
+            "regular_price": format_price(self.regular_cents),
+            "currency": currency,
+            "mode": self.mode,
+            "fixed": self.fixed,
+            "percent": self.percent,
+            "has_discount": self.has_discount,
+        })
+    }
+}
+
+/// Resolve one submitted option into the sale price to store. `Ok(None)` clears
+/// the discount; `Err` is an i18n key for the validation message.
+fn resolve_row(
+    regular_cents: i64,
+    mode: &str,
+    fixed: &str,
+    percent: &str,
+) -> std::result::Result<Option<i64>, &'static str> {
+    let sale_cents = if mode == "percent" {
+        if percent.is_empty() {
+            return Ok(None);
+        }
+        let pct = parse_percent(percent).ok_or("discount-invalid")?;
+        if pct <= 0.0 || pct >= 100.0 {
+            return Err("discount-percent-range");
+        }
+        percent_to_sale_cents(regular_cents, pct)
+    } else {
+        if fixed.is_empty() {
+            return Ok(None);
+        }
+        parse_price_to_cents(fixed).map_err(|_| "discount-invalid")?
+    };
+    if sale_cents <= 0 {
+        return Err("discount-must-be-positive");
+    }
+    if sale_cents >= regular_cents {
+        return Err("discount-below-regular");
+    }
+    Ok(Some(sale_cents))
+}
+
+async fn discount_view(
+    v: &TeraView,
+    jar: &CookieJar,
+    product: &products::Model,
+    rows: &[DiscountRow],
+    audience: &str,
+    error: Option<&str>,
+) -> Result<Response> {
+    let rows_json: Vec<_> = rows.iter().map(|r| r.to_json(&product.currency)).collect();
+    let has_discount = rows.iter().any(|r| r.has_discount);
+    format::view(
+        v,
+        "admin/catalog/discount_form.html",
+        json!({
+            "product": {
+                "id": product.id,
+                "name": product.name,
+                "currency": product.currency,
+            },
+            "rows": rows_json,
+            "audience": audience,
+            "has_discount": has_discount,
+            "error": error.map(|e| e.to_string()),
+            "lang": current_lang(jar),
+        }),
+    )
+}
+
+#[debug_handler]
+async fn discount_show(
+    auth: auth::JWT,
+    jar: CookieJar,
+    ViewEngine(v): ViewEngine<TeraView>,
+    Path(id): Path<i32>,
+    Query(params): Query<HashMap<String, String>>,
+    State(ctx): State<AppContext>,
+) -> Result<Response> {
+    guard::current_admin(auth, &ctx).await?;
+    let audience = read_audience(&params);
+    let product = product_by_id(&ctx, id).await?;
+    let variants = product_variants::Entity::for_product(&ctx.db, id).await?;
+    let rows: Vec<DiscountRow> = variants
+        .iter()
+        .map(|variant| DiscountRow::from_db(variant, audience))
+        .collect();
+    discount_view(&v, &jar, &product, &rows, audience, None).await
+}
+
+#[debug_handler]
+async fn discount_update(
+    auth: auth::JWT,
+    jar: CookieJar,
+    ViewEngine(v): ViewEngine<TeraView>,
+    Path(id): Path<i32>,
+    Query(params): Query<HashMap<String, String>>,
+    State(ctx): State<AppContext>,
+    body: String,
+) -> Result<Response> {
+    guard::current_admin(auth, &ctx).await?;
+    let audience = read_audience(&params);
+    let product = product_by_id(&ctx, id).await?;
+    let variants = product_variants::Entity::for_product(&ctx.db, id).await?;
+
+    let pairs: HashMap<String, String> = form_urlencoded::parse(body.as_bytes())
+        .into_owned()
+        .collect();
+
+    // Resolve every option before persisting anything, so one bad row can't leave
+    // the product half-discounted. On the first error, repaint with the inputs.
+    let mut resolved: Vec<(product_variants::Model, Option<i64>)> = Vec::new();
+    for variant in &variants {
+        let row = DiscountRow::from_submitted(variant, audience, &pairs);
+        match resolve_row(variant.price_cents, &row.mode, &row.fixed, &row.percent) {
+            Ok(value) => resolved.push((variant.clone(), value)),
+            Err(key) => {
+                let rows: Vec<DiscountRow> = variants
+                    .iter()
+                    .map(|v| DiscountRow::from_submitted(v, audience, &pairs))
+                    .collect();
+                return discount_view(&v, &jar, &product, &rows, audience, Some(key)).await;
+            }
+        }
+    }
+
+    let txn = ctx.db.begin().await?;
+    for (variant, value) in &resolved {
+        let mut active = variant.clone().into_active_model();
+        set_value(&mut active, audience, *value);
+        active.update(&txn).await?;
+    }
+    txn.commit().await?;
+    list_redirect(audience)
+}
+
+#[debug_handler]
+async fn discount_remove(
+    auth: auth::JWT,
+    Path(id): Path<i32>,
+    Query(params): Query<HashMap<String, String>>,
+    State(ctx): State<AppContext>,
+) -> Result<Response> {
+    guard::current_admin(auth, &ctx).await?;
+    let audience = read_audience(&params);
+    let _product = product_by_id(&ctx, id).await?;
+    let variants = product_variants::Entity::for_product(&ctx.db, id).await?;
+    let txn = ctx.db.begin().await?;
+    for variant in &variants {
+        let mut active = variant.clone().into_active_model();
+        set_value(&mut active, audience, None);
+        active.update(&txn).await?;
+    }
+    txn.commit().await?;
+    list_redirect(audience)
+}
+
 pub fn routes() -> Routes {
     // Several images may be uploaded in one submission; allow a generous total
     // (per-file size is still capped at IMAGE_MAX_BYTES while reading).
@@ -764,4 +995,16 @@ pub fn routes() -> Routes {
             post(update).layer(image_limit),
         )
         .add("/admin/catalog/products/{id}/delete", post(delete))
+        .add(
+            "/admin/catalog/products/{id}/discount/edit",
+            get(discount_show),
+        )
+        .add(
+            "/admin/catalog/products/{id}/discount",
+            post(discount_update),
+        )
+        .add(
+            "/admin/catalog/products/{id}/discount/remove",
+            post(discount_remove),
+        )
 }